PARIS: Biologists have reported the discovery of a spectacular species of giant lizard, as long as a full-grown man is tall, and endowed with a double penis.

The secretive but brightly coloured monitor lizard is a closecousin of the komodo dragon of Indonesia. Unlike its relative, however, it neither kills to eat nor feasts on carrion. It is entirely peaceable and fruit-eating.

Dubbed Varanus bitatawa, the lizard measures two metres in length, says an account published by the Royal Society.

It was found in a river valley on northern Luzon in the Philippines, surviving loss of habitat and hunting by local people who use it for food.

How many of the lizards have survived is unclear. The species is almost certainly critically endangered, and might well have disappeared without being catalogued had not a large male specimen been rescued alive from a hunter last June.

Finding such a distinctive species in a heavily populated, highly deforested location ‘’comes as an unprecedented surprise’’, say the authors, writing in the journal Biology Letters.

The only comparable recent finds are the Kipunji monkey, which inhabits a tiny range of forest in Tanzania, and the Saola, a forest-dwelling bovine found only in Vietnam and Laos.

V. bitatawa has unique markings. Its scaly body and legs are a blue-black mottled with pale yellow-green dots, while its tail is marked in alternating segments of black and green.

Males have a double penis, called hemipenes, also found in some snakes and other lizards.

The two penises are often used in alternation, and sometimes contain spines or hooks that serve to anchor the male within the female during intercourse.

V. bitatawa has a relative in southern Luzon, V. olivaceus, but the species are separated by three river valleys and a gap of 150 kilometres and may never have met.

One reason the lizard has gone undetected, the researchers speculate, is that it never leaves the forests of its native Sierra Madre mountains.

The authors say it should become a "flagship species" for efforts to preserve the remaining forests of northern Luzon.